As I've previously (and repeatedly) observed, Canon's mirrorless will bridge (and presumably cannibalize) their high-end P&S line and the Rebel line.
If it's APS-C, it's a given that it'll take EF-S lenses at the least, and the Shorty McForty strongly hints that it'll take regular EF lenses as well. Considering that there won't be a mirror to get in the way and that that's the reason you can't mount EF-S lenses on EF cameras, the new mirrorless being able to mount EF lenses would almost seem to be a given.
I think the only remaining question will be if Canon introduces a new, even more compact lens series that still uses the EF physical mounts but moves even more of the optics farther back into the body. That might let them design something as pocketable as many are clamoring for -- say, a slow kit zoom not much bigger than the Shorty McForty. They might also take this opportunity to introduce in-camera IS to further save on lens size
But, again -- mirrorless will never encroach on the pro line any more than EF-S has. And if the new mirrorless comes introduced with a new lens that can't be mounted on EF-S, then it's guaranteed that there'll never be a Canon mirrorless with any size sensor other than APS-C.
I think the Canon lineup will eventually look mostly something like this:
PowerShot - Pocketable P&S, many many models, no significant change from today
Mirrorless - Replaces G-series PowerShots and all Rebels, 3 - 5 models total
??D - APS-C DSLR, one model, replacing both the 60D and 7D
5D - Full-frame DSLR w/o integrated grip, one model
1D - Flagship model
...plus whatever pro video stuff they do like the 1DC
The interesting questions will be whether they add an entry-level full-frame camera (I'm guessing they won't) and what their insane megapickle camera will be (I'm guessing a 1 series something-or-other that puts the D800 to shame but also costs at least half again as much).